Russia and NATO agreed to formulate terms for missile defense cooperation by June 2011.

"We could cooperate one day in shooting down missiles," Rasmussen said.

The NATO-Russia Council, which met in Lisbon, also agreed to resume theater missile defense exercises and continue cooperation on the joint assessment of ballistic missile threats and the fight against sea piracy.

Rasmussen described the meeting as a "true, fresh start" to the relationship, adding that the 29 members of the council shared important interests and the "same threats" to their security.

NATO has officially invited Russia to participate in the creation of a missile defense shield in Europe, the alliance said in its summit declaration adopted on Saturday.

"We have decided to develop a missile defense capability to protect all NATO European populations, territory and forces, and invited Russia to cooperate with us," it said.

NATO will continue to explore opportunities for missile defense cooperation with Russia in a spirit of reciprocity, maximum transparency and mutual confidence.

"We reaffirm the Alliance's readiness to invite Russia to explore jointly the potential for linking current and planned missile defense systems at an appropriate time in mutually beneficial ways," the declaration said.

The alliance is also prepared to engage with other relevant states, on a case by case basis, to enhance transparency and confidence and to increase missile defense mission effectiveness.

Russian Foreign Minister Sergei Lavrov said earlier this month that a joint missile defense system was "completely feasible."

Moscow has retained staunch opposition to the deployment of missile-defense systems near its borders, claiming they would be a security threat. NATO and the United States insist that the shield would defend NATO members against missiles from North Korea and Iran and would not be directed at Russia.